Re: [RFC][PATCH 2/2] perzone slab LRUs

[Nick Piggin <nickpiggin@yahoo.com.au>]

Martin J. Bligh wrote:

>>Oops, forgot to CC linux-mm.
>>
>>Nick Piggin wrote:
>>
>>>This patch is only intended for comments.
>>>
>>>This implements (crappy?) infrastructure for per-zone slab LRUs for
>>>reclaimable slabs, and moves dcache.c over to use that.
>>>
>>>The global unused list is retained to reduce intrusiveness, and another
>>>per-zone LRU list is added (which are still protected with the global 
>>>dcache
>>>lock). This is an attempt to make slab scanning more robust on highmem and
>>>NUMA systems.
>>>
>
>Do we have slab that goes in highmem anywhere? I thought not .... 64 bit
>NUMA makes a lot of sense though.
>
>

I don't think so, but it still (I think) allows a general slab pressure 
forumula
for highmem and muliple ZONE_NORMAL NUMA that doesn't blow up like our 
current
one can.

The per-zone lists I'd say would have to help somewhat on the 
performance side of
things as far as not taking remote cache misses during scanning. It 
should also
mean that a low memory node will not globally shrink masses of slab from 
nodes that
have plenty of memory.

As far as the dependant inodes problem goes - it could be a significant 
problem,
and I think would need to be solved before perzone slab LRUs are a 
viable option.
The most simplistic way I can see to solve it is: if we scan an inode 
that is pinned
by dentries, scan its pinning dentries instead.

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